# Questions tagged [mathematics]

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### Estimating real world object distance from photo

I'm not really sure if this is possible but it should be. I currently have a photo of a sphere, whose radius I've measures physically. Knowing the apparent size of the sphere from the photo and all ...
125 views

### Fastest way to put a point on the circumference of a circle

My goal is to take a point that is inside of a circle with a given radius and put it on the circumference. Recently I have been normalizing the vector between the point and the center of the circle ...
70 views

### How can I draw a tube on basis of position and angle between two 3d points?

I'm struggling with this idea of creating two particles in 3d and draw a tube between them. I can't figure out how to properly set the angle of the tube. I've used two approaches: calculating the ...
617 views

### Object rotating around origin instead of object center?

I am implementing simple rotation but the object is not rotating around the local center instead it is rotating around world origin. This is the code: ...
371 views

### Why does substracting -1 in shader fail for a float data type?

I am loading a texture in a WebGL fragment shader (GLSL version 1.00). This is my working code: ...
246 views

### Unwinding an image on a spiral to make it long and flat

Here's an odd intellectual puzzle. Something I was daydreaming about on a train - but the maths are somewhat beyond me. How would someone go about un-winding a spiral to produce a long flat image? ...
309 views

### Generate this kind of 2d burst or pulse algorithm?

I'm currently trying to develop a game using Cocos2d-x using C++. I really need to generate this burst or (donut-shaped) pulse. I'm having a difficult time how to generate such shape. At first, I was ...
643 views

### Line segment intersection test and find the point of intersection

Thanks for the suggestions. Now I am doing it as follows: First off it is identified if two line segments intersect or not. And I am using the algorithm described in the book - "Introduction to ...
210 views

### Find the longest straight line between two points on surface of polygon

My shape is a slightly concave polygon, and I'd like to know the maximal diameter. I imagine a straight line between two points on the surface of the polygon, such that the line does not pass outside ...
219 views

### Sine-based Tiled Procedural Bump

I am trying to implement this formula to generate bump but I am facing some issue. The result doesn't look the same it's much darker. Here is my result (without same parameters) but it is much darker ...
935 views

### OpenGL C++ Camera Rotation Problem

Currently for a university assignment I have been given a 3D rendering engine, capable of rendering a 3D world. One task is to create a first person camera for it (I know with OpenGL you don't have a ...
54 views

### Making surface with common parametrization from bunch of other surfaces

I have bunch of surfaces, like in these two images: Currently to make single surface with common parametrization I sample points uniformly from all source surfaces, and fit single NURBS surface from ...
272 views

### Moving each point of a surface in direction of corresponding normal

So let assume that I have some convex smooth and unclosed surface. I'm moving each point of it in a normal direction by some constant factor (This factor is same for all points on surface). Can I ...
143 views

### intersection between line segments - narrowed precondition

I believe that the issue may already have been discussed here. I want to find if two line segments does intersect and if they do then find and store and intesection points. Now it is already confirmed ...
467 views

### How to invert an affine matrix with small values?

I'm using an affine transformation matrix to transform 2D coordinates from screen (magnitude 10e3) to small parts of fractal sets (magnitude as little as 10e-15). I also need to map the other way ...
667 views

### Rotate line around center

I have to use a propriertary graphics-engine for drawing a line. I can rotate the whole drawing by its origin point (P1). What I want, is to rotate it around its center point(M). So basically that it ...
1k views

### OpenGL with SFML, create an n-pointed star?

Completely stuck on how to do this. Yes, it is a homework problem, but its the first we've had in the class so not too familiar with graphics. Also, seeing as its homework, please don't just give the ...
2k views

### What makes a good permutation table?

I'm implementing improved Perlin noise. Its key feature for randomisation is the hardcoded permutation table, which gives essentially random but reproducible gradients at the cells of the grid. The ...
622 views

### Ray tracing - tangent space for a point on a sphere

In a ray tracer, given a point on a sphere (point_of_intersection with a ray) and its normal for that point (point_of_intersection - center_of_sphere) how do I calculate the tangent space for that ...
57 views

### Compute angles and thereby endpoints in a raster grid?

I am at the moment having some issues with computing an endpoint in a raster grid that is also a valid position in a graph. I am trying to draw a line between these two points, but as the point I am ...
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### Draw angles lines in raster graphics using bresenham line algorithm

I at the moment trying to draw some angled lines using bresenham line algorithm which can circulate a 2d array of size 21x21, as a line angled from 0 - 2pi. So the idea is that the program has to ...
819 views

### Is my perspective math correct?

I've got a homework in which I have to calculate and plot some points using a pespective transformation, but I'm not sure my results are correct, since the 3d plot using Camera coordinates looks very ...